Hydeauijcally operated pitch chang



March 13, 1945. H. H. ROBY' A2,371,187

HYDRAULICALLY OPERATED PITCH CHANGING'MECHANISM March 13, 1945.

Filed May 1, 1942 -5 Shee'ts-Sheet- 2 ./Zcd 30 INVENTOR.

Horace @obj ATTORNEY.

March 13, 1945. v H. H. ROBY 2,371,187

HYDRAULICALLY OPERATED PITCH CHANGING MEHANISM Filed May l, 1942 5Sheets-.Sheet 5 2M Honda@ '9' V BY gd /g Patented Mar. 13, 1945HYDRAULICALLY OPERATED PITCH CHAN G- ING MECHANISM Horace H.Roby,'Wicl1ita, Kans., assigner, by mesne assignments, to Robert C.Foulston, W. L. Hartman, and John F. Fitz-Gerald, trustees of Roby,Inc., Wichita, Kans., a oorporation of Kansas Application May l, 1942,Serial No. 441,346 3 claims. (ci. 17o-163i c onditions of air density,plane speed, engine speed and power, etc. These conditions varydepending upon whether the plane is taking oiI or flying level at asubstantial altitude. Indeed, these conditions may vary considerablyduring the course of a long flight depending upon the weatherconditions, ,the character of the country over which the plane is dying,etc. Accordingly, fixed pitch propellers are generally unsatisfactory.It is highly desirable that an adjustable pitch propeller be providedhaving a maximum and aminimum pitch position and capable of being heldat any selected adjusted intermediate position.

For example, it is desirable that the propeller blades be adjusted to alow pitch during the takeof! period and adjusted to a high pitchposition after the plane has gained altitude and assumed a normal levelflight. If the propeller blades are given a low pitch during thetake-off, the engine can obtain its most efllcient speed substantiallyimmediately, permitting the plane to rise after a relatively short runand to gain elevation essentially rapidly. When takingofl, the planespeed is low and there is a heavy load on the propeller. Internalcombustion engines do not develop maximum power at slow engine speeds.Therefore, if

,y `during the take-oil period the pitch of the blades is too high, theresistance offered by the airto rotation of the propeller will hold theengine to a relatively slow speed so that it will be most inf eiilcientwhen the greatest power is needed. Also, if the pitch of Ythe propellerblades is too high during thetake-oil period, the plane will remain. onthe ground a longer time before attaining iiying speed. v Itisespecially desirable in the case of lightI airplanes and observation,in-v terceptor, scoutingand fighterplanes that the take-otr time bereduced to a minimum.

,It the propeller is adjusted and held at a low pitch position, theplane will'rise and attain flyjusted to a high pitch position duringnormal night. The propeller blades will then offer sum cient resistanceto hold the'engine at its normal full power speed. e

Furthermore, present day airplanes fly long distances and frequently athigh altitudes. When the plane is operated under these conditions, it isoften necessary that the propeller blades be held at intermediatepositions between the maximum and minimum pitchl positions ii optimum emciency is to be realized.

Variable pitch propellers are operated both mechanically andhydraulically. When a mechanical control is used, the propeller bladesmay be rotated through a predetermined pitch range andheld at a selectedadjusted position. However, where a hydraulic control is used, it hasnot been possible to easily position andhold the propeller blades at anyselected adjusted intermediate pitch position.

It is .therefore an object of my invention to provide a hydrauliccontrol for a variable pitch propeller that may be manually operated tohold the propeller in any selected adjusted position between a maximumand minimum pitch position.

Another object of my invention is, to provide a hydraulic control o! theabovementioned character that may be easily operated by the pilot whenthe plane is in ight.

Still anotherobject of my invention is to provide a hydraulic controloi' the above mentioned character that involves a minimum of workingparts to eliminate mechanical troubles as far as possible. i

Other objects and advantages of my invention4 will be apparentl duringthe'course of the following description. i

In the accompanying drawings forming a part the same,

ing speed after a relatively short run. However,

after the plane assumes a normal level iiight, the resistance oieredbythe air to propeller rotation is decreased, the load on theenginebecomes less and the engine will speed up.. `The engine must then beythrottled down and will produce Vbut a portion of the power of which itis capable. For maximum emciency, the propeller should be ad- Fig. l isa side elevation of a hydraulically operated pitch changing mechanismembodying my invention, parts beingl shown in section for clear,- nessof illustration,

' Fig. 2 is a fragmentaryv vertical sectional view,

taken on the line 2-2 ot Fig. 1,

the line 5 5 of Fig. 3, showing an automatic fluid control valveembodying a part ot my invention.

between.

line 8-6 of Fig. 5. l Fig. 7 is a fragmentary vertical sectional viewtaken on the line 1-1. of Fig. 6, showing a cam comprising a part of theautomatic valve mecha- Y nism in a position to close the valve,

Fig. 8 is a view similar to Fig. 7 but showing the cam rotated to aposition to open the valve, and

Fig. 9 is a fragmentary view similar to Fig. 3,v

ends of the shanks 20a,v and bearing surfaces for rotation of thesleeves on the spindles is supplied by removable bearing sleeves.Collars 2| have flanges 2la within the housing Il. Thnist'bearings 22are positioned between flanges Ila and the enclosing ends ila of housingIl. These thrust bearings carry the centrifugal loadimposed when thepropeller is rotated. The thrust showing the hydraulically operatedpitch changing mechanism without the automatic fluid control valve. i

In accordance with this invention, I mount-a variable pitch propeller ona conventional crank shaft having a hollow outboard end as shown in Fig.l. Mechanism is provided for rotating the propeller blades about theiraxes in response .to movement of a piston mounted on the forward end ofthe crank shaft. A bleedr line from the lubricating system of the planeconducts crank case oil into the hollow crank shaft. The pressuredeveloped by the oil pump on the fluid in the crank shaft is suilicientto force the piston outwardly against the forces -acting on the rotatingpropeller blades. A valve manually operable from the cockpit of theplane controls the` flow of oil into the crank shaft and also the flowyof oil therefrom. By proper operation of the valve, a. requisite amountof oil may be forced into the hollow portion of the crank shaft to movethe piston a selected distance. An automatic valve mounted in the crankshaft is provided to hold the oil in the piston.` The automatic valve isoperated by fluid pressure in the crank shaft.l

Each time fluid under pressure is injected into the crankshaft, thevalve is automatically operated. One injection lof fluid into the crankshaft moves the automatic valve to a closed position and the nextinjection of uid into the crank shaft moves the valveto an openposition.' Thus,

repeated opening and closing of the manually operated valve will causeconsecutive injections of duid into thecrank shaft so that the automaticvalve may be either opened or closedtc either hold orreleasc the oil inthe piston. When the automatic valve is closed, the oil is trapped inthe piston. When thegautomatic valve is open, oil 'trapped in thepistonV is released. The torque on the propeller blades will thenretract the pisbearings also permit axial rotation of the propellerblades about spindles l2a when the pitch of the blades is changed.

y Helical springs 23 are confined between the shoulders i2b of spindlesI2a and-the shoulder 20h ofthe ,outer bearing sleeves. The resilientaction of springs 23 urges the propeller blades outwardly and holds thecollar flanges 2 la against the inner races of thrust bearings 22..'Heretofore, it has been customary to use roller bearings in place ofsprings 23. However, where roller bearings are used. it is necessary toprovide for removing play in the bearings by means of shims. Thisbearing arrangement has proven to be generally unsatisfactory. When aroller bearing assembly of the type shown at 22 is not furnished withresilient vmeans to hold it compactly together, vibrations' created bylpower impulses of ythe engine cause the balls ofthe race to chatter andwear the surfaces of the inner and outer races. Thus, the balls poundthemselves4 into the races and a rough bearing is the result. By usingsprings 23, it is unn to "shim" the bear-l ings with sumcient force toprevent chatteringv or vibration of the balls. Springs 23 also preventthe nanges 2I'a from dropping a'way from thrust bearings 22 4when the.propeller is at rest.

Surrounding .the bases of spindles' Haare ringshaped control arms 2l.-These arms are journaled for rotative movement`about pivot pins 25which are partially embedded in the hub I2. The arms loosely surroundthe spindles andv the ends thereof adjacent pivot pins 2l arebifurcatedto receive pins 28 projecting from the flanges 2Ia ofthe propellercollars as shown in'Flg. 2. When the control arms are pivoted aboutpins. 25, they will move the propellers through an arc having the centerof the pivot pins 2l as a radius.' This/ movement will increase ordecrease the pitch of ton and-.unless checked blades willeontinuetorctate nntiltheyassmneaminimum pitchposition. Inthepreferred'"tofmyinventlon" shown m the nimm-Is designates' a tubular ycrankshaftwhicnprojects-'through Y the front wall ofcrank case lijn-theconventional manner. A propeller hub lspllned to fcrankshaft'llasbestshowninlll 'end of hub' I2 seals again-st sufficeof'holdingringheldinpoeitionbyspacingrlngi' '|3a. A'sealingringl3bfsinfrontofring- I3. f Aconeorhcidingrlng'llisheldtlshtlylgsinst.

the intermicpnoiaal msoe'lsat the :mma

I3 and lochngring Il Il there- Ahollowcylind'ricalhousin'gl'liscarrledbypropellerh'nb. Thelsformedintwo partswhichareheldtog'etherbybolts I3 andnutsll. llaresecuredtothebuttends of the propeller blades (not shown).on the threadedpormsodshanksaofsleevesare screwedcollars. Thelmallhas'integml the blades. Mounted on a forward tubular extension I2c ofthe hub l2 is apiston 2l. Arms2'la integral with the piston are fittedinto channels or grooves |2d in the hub and serve to connect with themds of control arms 2l remote from pivots 25 through pins 23 fastened tothe arms by screw bolts shown dotted in Fig. 2. When the piston movesoutwardly due to the introduction ofhydraulicliquidfthecuntrolarmswillbeplvoted about pins 2l to increasethe pitch of the propeller blades. when the piston. moves inwardly upondischargeof hydraulic liquid, control armsv 2l will be pivoted in theopposite direction about pivot pins 23 to decrease the pitch of theblades.

Anendmclosurethreadedintothetubular extension 12e carries s-flexiblegrlng 3l which sealstheinnerwalloftheplstontoformafluidvTheipistonlslimitedin-itsmovement b y bolt 3|. end c! boltf3l extendsthroughtheend'otthelistonnndhasahea'dfor adjustment. 23amthe'endmcloslne23 around'thepermitthehydraulicfluidto-Av enterthepiston.Hydraulicmewltlnnthe pistonwlllforeeitoutwardlymtlltheheadof boltllThem#- l'ldllljplndl Iwhichmjectintqthehollow '7ltmlbpk'eiln'guhedbyldjmtdboltll.

by lock nut 52.

Thus, the stroke of the piston-.may be easily acuda? The boit is heid' mthe selected smashed positions sleeve.

regulated without dismantling any parts of the mechanism. Inward"movement of the piston is limited by abutment of bosses 33 and 34 inwhich position the hydraulic fluid may freely pass through radialchannels 34a thus preventing the formation of a seal between the pistonand end enclosure 29.

the action of spring 52. When the uid pres- As a source of hydraulicuid, oil from the lubricating system is supplied under pressure to thepiston by pump 35. This oil pump is conventional in airplanes tocirculate the fluid lubri-l cant from a reservoir or sump through thelubricating system. A fragmentary part of the oil circulating system isshown at 3B. Oil is bled from the line` through pipe 31. This oil passesthrough valve 35, pipe 39, passage and into the hollow crank shaftthrough radial passages loa. The core 35a of valve 55 ismanually rotatedby control arm 4|. A link 42 connects the arm 4i with a control on theinstrument board (not'shown) within the cockpit of the airplane. Thecontrol is preferably locatedin a position 4 where it may-be easilyoperated by the pilot.

When arm 4I is pushed forwardly, -as shown'in `Fig. l, passage 35hthrough the valve core will connect pipe 31 -with pipe 39 so that pump35 forces ol under pressure into the crank shaft. If arm 4I is moved ina reverse direction, the enlarged end of passage 38h will move intoreg'- ister with pipe 39 and pipe 43. Pipe '43 connects valve 35 withthe oil sump. When the valve core' is in the last mentioned position,pipe 31 is shut cifand fluid trapped in the crankshaft and behind thepiston will `flow through passage 45, pipe 39, valve passage 38h, andpipe js to theoil sump or reservoir.

. Flowi of oil to orfrom piston 21'through the. crank shaft iscontrolled by avalve designated generally by the numeral 44 having atubular valve body 45. The forward end of a valve body is fixedlylconnected to' a boss on the hub endl enclosure 29. A bearing seal lsupports theA inner end of the valve body against the internal wall ofthe crank shaft. The valve body is formed in two parts 45a and 45b'whichare connected by a valve plug 41 shown in Fig. 5, The valve plug has alongiiudinal passage 41a which is normally closed by ball valve 45'.Helical sure inthe crank shaft is cut on by operation of valve ",spring52. slides the plunger inwardly against locking ring i53. Eachreciprocating of plunger 5i rotates camf54 ninety degrees. Ro-

tation of the cam actuates the pin to unseat l and permit seating of theball valve 48.

Referring now to Figs. 5 through 8 where is best shown the manner inwhich the cam 54 is operated and the rotative actuation of the ratchets51 and 55 and-explaining the operation of the valve 44 assuming the camin the position shown in Figs. 5 and '1, the manual control valve 39 in.the position shown in Fig. 1 and that hydraulic fluid is beinginjected..by pump 35; the plunger 5i is moved outwardly by introductionof hydraulic fluid. Abutment 5Ic during this movement ofthe plunger 5i.contacts the adjacent tooth of ratchet 5 5 rotating the ratchet and camforty-ve degrees from that shown in Figs. 5 and 1 to `a position shownin Fig. il.V As suggested,

the teeth of ratchets 51 and 55 are staggered.

l When the uid pressure upon valve 5i is vreleased by'movement ofcontrol valve 35 to connect pipes 39 and 43, the hydraulic fluid movesfrom'the crankshaft toward the sump. Spring 52 urges plunger 5iinwardlyand abutment 5Ib engages the adjacent tooth of ratchet 51rotating cam 54 ari'additional forty-five degrees orto a hori.

zontal position parallel with pin 55 when ball 'valve 45 is at itsmaximum open position. t

With every injection of hydraulic fluid, plunger ,El is forced outwardlyagainst the action of spring 52 and with release of pressure on thehydraulic fluid, plunger 5i moves in a reverse direction due to actionvof the spring. Both out# ward and -inward movements of plunger 5i causea forty-five degree rotation of the cam 54, the

combined reciprocation causing a ninety degree rotation of the cam dueto positioningof the abutments 5lb and 5Ic and the staggered arrangementof the ratchets 51 and 55. As the 'cam rotates to the forty-:liveAdegree position spring 49 conned between plug 55 and ball valve 4s urgesthe ball valve' to a seated position.

To unseat the ball valve there is located inwardly of plug 41 and withinvalve body 45 a plunger 5|l connected by a restricted neck to hollowopen ended reciprocating sleeve 5in shown rectangularin cross sectioninvFig. 6. A sleeve extension of plug 41 extends into the end of therectangular sleeve 5ia' and is surrounded by compression' spring 52which abuts itsouter end on plug 41 andits' inner end on reciprocatingsleeve 5Ia. Within the rectangular' reciprocating sleevev 5la is a cam54 keyed to a pin- 55 between two ratchets 51 and 55. These ratchetshave four teeth positioned ninety degrees apart and are shown in Fig. 8,it will slide pin 55 to move ball valve 45 away from its seat. The-fluidthen iiows from the hollow. crank shaft chamber around loosely fittingplunger 5l, through slots 45e in the valve body, through ports 41b inplug 41, around the unseated ballvalve 45, through passages 41c and 25aand behind 'piston 21.

After the piston has been moved outwardly a distance sumcient toincrease the pitch of the propeller bladesa. desired amount, it will'benecessary to close vthe |ball' valve 45 and hold the hydraulic fluidbehind the piston. To effect th's result. manually' operated valve 55must be actuated one time more to move the cam through vninety-degreeswhen the cam 54 is again in va vertical position as shown in Fig. 5 andball valve 45 is closed. f

Should the pilot desire the propeller pitched to its maximum, movementof the control valve 55 to permitadrnlssion ofthe hydraulic. fluid willaccomplish this result. If va minimum pitch or feathering'of the bladesis desired, this is effected by operating the manual control I5 so thehydraulic fluid will drain'back into the sump or reservoirand thisresultis obtained when the cam 54 is in a horizontal position and bailvalve wise and for the same reason, increasing the pitch is a relativelyslow operation permitting actuation of the control valve 33 at any timeto give the propeller blades a selected pitch. To maintain the pitch ofthe. propeller in any ilxed selected position, the operation is thatheretofore described, namely the hydraulic iluid is introduced untilpiston 21 by means of arms 21a has moved the blades to the desiredpitch. Control valve r38 is then actuated to rotate the cam to aposition where ball valve 48 is closed and the iluid is trapped behindthe piston.

Attention is directed to the fact that the automatic valve M is centeredwithin the crank shaft so that every moving part oi the valve operatesalong the center of the crank shaft. Thus, none of the parts will beinfluenced by centrifugal force.

If it is desired to have only two selected pitch positions of thepropeller blades, one for taking on and the other for normal cruising,the hydraulically operated valve 44 may be omitted.`

Fluid pressure inthe crank shaft `and behindv piston 21 will then bereleased. The wind resistance acting on the propeller blades willprovide suillcient torque to move piston 21 inwardly and expel thehydraulic fluid therein. After the plane gains sufficient altitude toassume normal level flight, the pitch of the propeller blades may beincreased to the maximum pitch position by operating the manuallycontrolled valve 3l to connect pipes 31 and 39. 'Ihe crank case oil,acting as the hydraulic iluid, is injected into the crank shaft by pump35. This iluid enters the piston and forces the same outwardly until itstravel is limited by engagement of bolt 3| with member 29. Valve 38remains open until it is again desired to reduce the pitch of thepropeller blades.

It will be readily appreciated, however, that the automatic valve 4l isa desirable 'feature for the reason that it may be used to hold thepiston 21 at a selected adjusted position between the inner and outerlimits of its travel. This is a decided advantage. When using valve M,should the propeller bladesY be in the maximum pitch position and theblades have been given too much pitch, piston 21 may be easily retracteda slight distance until the propeller blades have the'proper pitch.

It may thus be'seen that I have achieved the 'o0 objects of myinvention. I have provided a hydraulically operated pitch changingmechanism for variable pitch propellers that may be easily operated bythe pilot. .By the use of my mechanism the propeller bladesmay be heldin any selected adjusted position bestsuited to existing conditions ofairdensity, plane speed and engine speed and power.

It is to be understood that the form of my invention'herewith shown anddescribed is to be taken as a preferred example of the same and thatvarious changes in the size, shape and arrangement of parts may beresorted to without departing from the spirit of my invention or thescope of the appended claims.

Having thus described my invention, I claim:

l. In combination with a variable pitch propeller, a hydraulicallyoperated pitch changing mechanism comprising a iluid pressure operatedmeans connected to the propeller blades for adlusting their pitch, amanually operated valve controlling the ilow of duid to and from theiluid pressure operated means, a iluid passage between the manuallyoperated valve and the fluid pres'- sure operated means, and anautomatic valve mechanism in said passage, said automatic valvemechanism including a rotatable cam adapted in diilerent adjustedpositions to open and close the automatic valve mechanism, and a fluidpressure actuated means operated by successive operations of themanually operated valve cooperative with the cam to move it to saiddifferent adjusted positions.

2. In combination with a variable pitch propeller, a hydraulicallyoperated pitch changing mechanism comprising a uid pressure operatedmeans connected to the propeller blades for adjusting their pitch, amanually operated valve controlling the ow of iluid to and from theiluld pressure operated means, a iluid passage between the manuallyoperated valve and the fluid pressure operated means, and an automaticvalve ymechanism in said passage, said automatic valve mechanismincluding a rotatable cam adapted in dierent adjusted positions to openand close the' mechanism in said passage, said automatic valvevmechanism including a rotatable cam adapted to open and close theautomatic valve mechanism, ratchet Wheels rotatable with the cam, and afluid actuated plunger having. pawls engageable with the said ratchetwheels to rotate. the cam.

HORACE H. ROBY.

